1. Field of the Invention
The invention relates to an exposure device for a imaging system, and more specifically to an exposure device comprising a straight row of substantially rectangular light-emitting elements LEDs, and a printer provided with such a straight row of LEDs.
2. Description of the Related Art
Exposure devices and printers of this kind are known from European patent specification 0 097 261, in which image formation is effected by means of a number of LEDs disposed in a straight row, these LEDs being imaged on a moving photoconductor via a Selfoc array. In order to increase the light yield, the LEDs are constructed in the form of elongated rectangles or parallelograms. The elongated LEDs are imaged as squares or diamonds by disposing a cylindrical lens between the row of LEDs and the photoconductor.
One disadvantage of these known devices is that the light distribution on the photosensitive medium is not uniform as considered in the direction of the row, there being a zone where there is distinctly less light formed between two image dots. In order that the photoconductor may nevertheless be fully exposed at these locations, it is necessary to increase the total light level, e.g. by increasing the LED energization current, as a result of which the heat evolution and the life of the LEDs decreases. Moreover, thin lines to be imaged will be completely over-exposed at the places where an increased amount of light falls, and thus these are no longer reproduced.